Tire non-uniformity relates to the symmetry (or lack of symmetry) relative to the tire's axis of rotation in certain quantifiable characteristics of a tire. Conventional tire building methods unfortunately have many opportunities for producing non-uniformities in tires. During rotation of the tires, non-uniformities present in the tire structure produce periodically-varying forces at the wheel axis. Tire non-uniformities are important when these force variations are transmitted as noticeable vibrations to the vehicle and vehicle occupants. These forces are transmitted through the suspension of the vehicle and may be felt in the seats and steering wheel of the vehicle or transmitted as noise in the passenger compartment. The amount of vibration transmitted to the vehicle occupants has been categorized as the “ride comfort” or “comfort” of the tires.
Tire uniformity characteristics, or attributes, are generally categorized as dimensional or geometric variations (radial run out (RRO) and lateral run out (LRO)), mass variance, and rolling force variations (radial force variation, lateral force variation and tangential force variation, sometimes also called longitudinal or fore and aft force variation). Uniformity measurement machines often measure the above and other uniformity characteristics by measuring force at a number of points around a tire as the tire is rotated about its axis.
Once tire uniformity characteristics are identified, correction procedures can be performed to account for some of the uniformities by making adjustments to the manufacturing process. Additional correction procedures can be performed to address non-uniformities of a cured tire including, but not limited to, the addition and/or removal of material to a cured tire and/or deformation of a cured tire.
Many different factors can contribute to the presence of uniformity characteristics in tires. For instance, tire uniformity can be affected by the tooling elements that are used in the manufacture of the tires. Exemplary tooling elements can include tire building drums, forms, molds, rollers and other tooling elements. Uniformity contributions from individual tooling elements can be difficult to identify using known uniformity analysis techniques, such as Fourier analysis techniques.
Existing techniques have been used to account for harmonic contributions of tooling elements, such as building drums, in green tire uniformity measurements used to predict after-cure uniformity for a green tire. For example, green tire uniformity waveforms have been analyzed to identify harmonic contributions of tooling elements to harmonic data, such as the first, second, third, and fourth harmonics of measured green tire radial run out. Such techniques do not identify a full tooling signature associated with a tooling element. Moreover, such techniques are typically used to discount uniformity contributions from tooling elements to the measured green tire uniformity waveform, such as building drum radial run out contributions to green tire radial run out measurements performed while the green tire is on the building drum.
Thus, a need exists for a system and method that can accurately identify tooling signatures for tooling elements, such as tooling signatures for individual building drums, forms, molds, rollers, and other tooling elements used in tire manufacture. A system and method that analyzes these identified tooling signatures and uses the identified tooling signatures to improve the uniformity of a tire would be particularly useful.